SergeModular

> What about one module which contains lowpass, highpass and coupler.

Something similar (and banana socketed) is the old Synton 3224 VCF

> I am often told (and seem to hear) the
> circuitry (vactrol) makes for very nice phasing sounds.

I just don't think it sounds very rich for tape phasing effects. I'm sure
it's excellent for other phase related functions.
CW